1. Field of the Invention
The invention generally relates to software emulation of optical communication networks, systems, nodes, modules and components.
2. Description of Related Art
Optical communication systems are a substantial and fast growing constituent of communication networks. The expression xe2x80x9coptical communication system,xe2x80x9d as used herein, relates to any system which uses optical signals to convey information across an optical waveguiding medium, for example, an optical fiber. Such optical systems include but are not limited to telecommunication systems, cable television systems, and local area networks (LANs). (Optical systems are described in Gowar, Ed. Optical Communication Systems, (Prentice Hall, New York) c. 1993, the disclosure of which is incorporated herein by reference.)
Many optical communication systems are currently configured to carry an optical channel of a single wavelength over one or more optical waveguides. To convey information from multiple sources, time-division multiplexing (TDM) is frequently employed. In TDM, a particular time slot is assigned to each signal source with the complete signal constructed from portions of the signal collected from each time slot. While this is a useful technique for carrying plural information sources on a single channel, its capacity is limited by fiber dispersion and the need to generate high peak power pulses.
While the need for communication services increases, the current capacity of existing waveguiding media is limited. Although capacity may be expanded (e.g., by laying more fiber optic cables), the cost of such expansion is prohibitive. Consequently, there exists a need for a cost-effective way to increase the capacity of existing optical waveguides.
Wavelength division multiplexing (WDM) is now a commonly utilized technique for increasing the capacity of existing fiber optic networks. WDM systems typically include a plurality of transmitters, each respectively transmitting signals on a designated channel or wavelength. The transmitters are typically housed in a first terminal located at one end of a fiber. The first terminal combines the channels and transmits them on the fiber to a second terminal coupled to an opposite end of the fiber. The channels are then separated and supplied to respective receivers within the second terminal.
The WDM system described in the previous paragraph can be perceived as a point-to-point connection with multiple signals carried from one terminal to the other. However, it is frequently advantageous to add and drop channels at various locations between the two terminals. Accordingly, other network elements, such as add/drop modules are often provided along the fiber in order to inject and/or remove channels from the fiber. Moreover, if the fiber extends over long distances, it is necessary to segment the fiber into sections with each fiber section being coupled to another by an additional network element that amplifies the signal (e.g., an erbium doped fiber amplifier).
In addition to the information bearing channels described above, Condict ""115 utilizes a service channel at a wavelength different than the information bearing channels and carrying diagnostic and span topology information that can also be transmitted through each span. Information associated with a span may be coupled via Ethernet connections to an internet protocol (IP) router. This IP router passes the information via the Internet to additional IP routers. A local area network (LAN) then transmits the information between the IP routers and to the network monitoring equipment. Finally, information associated with a span is similarly passed to network monitoring equipment through Ethernet links and an IP router.
The Condict ""115 patent ensures proper operation of the WDM system by monitoring each network element. In the event of a failure, such as a fiber break, the communication system maintains its ability to monitor each network element by using, for example, a service channel separate from the main optical communication channel. Moreover, the communication system automatically responds to a fault by having each network element identify itself and report information about its operating status. Optical communication networks typically include an optical communication path and a plurality of network elements coupled to the optical communication path. The network elements typically include one or more optical, opto-electrical, electro-optical, or electrical components. A microprocessor-based controller (a.k.a. node control processor (NCP)) runs management and control software that manages, tracks and/or controls various functions of the node hardware.
In other words, the NCP may monitor and/or control hardware components of the node in order to maintain the functionality, tune performance and otherwise manage the optical network. For example, the status of a first optical component may be monitored by the first processor that generates a first electrical signal in accordance with the status of the first optical component. This status info may be used by the controller or transmitted to other controllers in the network in order to manage the component, the node, other components, other nodes, the network, etc. A service channel (e.g. in-band or out-of-band wavelength) is typically used to transmit such status and other management information.
Some of the challenges facing optical communication equipment vendors include development, testing and verification of components, nodes and systems. These tasks are made even more challenging, if not impossible, when the hardware is not available. In other words, some or all of the hardware components in a node may not be available to software engineering and testing groups due to production constraints, unavailability of components, prior commitments to customers, etc. The management and/or control software being written for these components and nodes, however, must be rigorously tested and validated before it can shipped to the customer. Without the necessary hardware to perform such tests, the software development and release may be delayed.
These problems are exacerbated by WDM systems, particularly high channel count WDM systems. For each channel there may be a set of hardware (e.g. transmitter, receiver, or other circuit packs) that is unique to that channel. As the channel count increases so does the number of corresponding circuit packs within network elements. Channel counts currently number about 100 but are expected to increase to several hundreds at least through product line and technology evolution. Thus, it becomes more and more cost prohibitive and logistically difficult to have full systems available in the quantities required for software application (i.e. agents) unit testing, software system integration, and validation testing particularly as the complexity of the system grows and various different types and versions of optical communications modules are developed. If not addressed, these problems potentially could affect product availability and product quality.
Thus, there is a need in the art for emulating certain hardware components of an optical communications so that the corresponding control and management software can be developed, integrated, tested and validated.
In order to address these problems, the invention was developed which emulates optical communications hardware and interfaces with nodal control processor(s) NCP(s). This emulator may execute on a workstation platform and emulate the optical behavior as well as appropriate communications hardware functionality so that the NCP may exercise functionality in a software development, integration or validation test environment.
In other words, the invention emulates optical networking hardware functionality to allow various levels of software application unit development, test and integration test without dependency on hardware availability.
The emulator is designed to execute in multiple modes to satisfy various diverse user requirements: single node circuit pack emulation, single span circuit pack emulation, and multi-span circuit pack emulation. All modes may be initiated from a common emulator setup/configuration mechanism that tailors the simulation session to the needs of the user.
More specifically, the invention may be characterized as a method of emulating the optical behavior of an optical communications system having a plurality of optical communications modules, including: generating a wavelength modeled object modeling at least a signal condition of an optical signal; generating a modeled object for each of the optical communications modules and including at least an optical power level field and a behavior modeling function modeling the optical behavior of the corresponding optical communications module; propagating the wavelength modeled object along a logical path of emulated optical communications modules; executing the behavior modeling function of the modeled object associated with the emulated optical communications module receiving the propagated wavelength modeled object; and storing the results of said executing in the associated modeled object.
The invention may also be extended to an optical communications system that includes a plurality of nodes. In such an implementation, the modeled objects are preferably organized into a plurality of nodes emulating the nodes of the optical communications system and the propagating step propagates a span modeled object between nodes, wherein the span modeled object includes the propagated wavelength modeled object.
The invention may also be extended to an optical communications system that includes a plurality of spans, each span having a plurality of nodes. In such an implementation, the modeled objects are preferably organized into a plurality of spans and nodes emulating the spans and nodes of the optical communications system and the propagating step propagates a multi-span modeled object between spans, the multi-span modeled object including the propagated wavelength modeled object.
The invention may also be extended to a wavelength division multiplexed system transmitting a plurality of optical signals at respective wavelengths. In such an implementation, the invention generates a plurality of wavelength modeled objects modeling at least the signal conditions and wavelengths of the optical signals; and propagates the wavelength modeled objects along a logical path of emulated optical communications modules.
The optical communications modules that may be emulated are many and varied and include an optical combiner combining at least some of the plurality of optical signals. If a combiner is present, the invention generates a combiner modeled object including an output signal power level field, the plurality of propagated wavelength modeled objects, and a combiner behavior modeling function modeling the optical behavior of an optical wavelength combiner; executes the combiner behavior modeling function and storing the results thereof in the combiner modeled object; and propagates the combiner modeled object to a next emulated optical communications module along the logical path of emulated optical communications modules.
The invention may also emulate an optical amplifier. In such a case, the invention generates an amplifier modeled object including an output signal power level field, an input power level field, pump power level field, the plurality of propagated wavelength modeled objects, and an amplifier behavior modeling function modeling the optical behavior of the optical amplifier; executes the amplifier behavior modeling function; and stores the results thereof in the amplifier modeled object.
Moreover, the behavior modeling function may not only perform mathematical calculations but also logical operations. An illustrative example is executing the amplifier behavior modeling function that includes overriding the signal conditions in the propagated wavelength modeled objects to Loss Of Signal if the value of the input power level field is less than a first threshold value or if the value of pump power level field is less than a second threshold value.
Executing the behavior modeling function may also include overriding the signal conditions in the propagated wavelength modeled objects to loss of frame if more than one transmitter modeled object has the same wavelength value.
The invention may also emulate an optical splitter feeding a plurality of optical receivers. In such a case, the invention generates a splitter modeled object including an output signal power level field, the plurality of propagated wavelength modeled objects, and a splitter behavior modeling function modeling the optical behavior of an optical splitter; generates a plurality of receiver modeled objects including an input signal power level field, a wavelength field, a signal condition field, one of the plurality of propagated wavelength modeled objects, and a receiver behavior modeling function modeling the optical behavior of an optical receiver; executes the receiver behavior modeling function and stores the results thereof in the receiver modeled object.
The wavelength modeled objects may further include a data rate field which permits the invention to execute a receiver behavior modeling function including overriding the signal condition in the receiver modeled object to loss of frame based on a determination of whether the data rate field of the propagated wavelength modeled object matches the data rate field of the receiver modeled object.
The execution of the receiver behavior modeling function may also include overriding the signal condition to Loss Of Signal in the receiver modeled object based on a determination of whether the signal condition field of the propagated wavelength modeled object indicates a signal unknown condition.
The execution of the receiver behavior modeling function may further include setting the input signal power level in the receiver modeled object to zero if the signal condition field of the propagated wavelength modeled object indicates a loss of signal condition.
The invention may also emulate an optical backplane and perform the execution step in an optical backplane emulator. In such an implementation, the invention maintains optical attributes at each of the emulated optical communications modules and updates at least one of the optical attributes when said executing step results in a change to a corresponding optical attribute field in the modeled object associated with said executing step. The execution step may also be performed by the emulated optical communications modules.
The invention is also capable of commanding a change in at least one of the modeled objects; executing the behavior modeling function in the modeled object changed by said commanding step; and storing the results of said executing in the associated modeled object.
The invention also includes a software emulation method for emulating the optical behavior of a system of optical communications elements of an optical communications system wherein the system includes hardware node elements and at least some of the hardware node elements include a nodal control processor and a bus, the method comprising: maintaining modeled objects for each of the optical communications elements being emulated wherein each of the modeled objects includes a behavior modeling function modeling the optical behavior of the corresponding optical communications element; receiving a first behavior event object trigger associated with a first emulated optical communications element; executing the behavior modeling function of the modeled object associated with the first behavior event object trigger; and updating the modeled object affected by the execution of the first behavior modeling function.
The inventive method may also include generating the first behavior event object trigger when at least one of the modeled objects has been received by the first emulated optical communications element.
The inventive method may further include maintaining optical attributes of the emulated optical communications elements; changing at least one of the maintained optical attributes of the emulated optical communications element affected by the execution of the first behavior modeling function; and sending a second behavior object trigger to the emulated optical communications element associated with the optical attributes changed by said changing step.
The inventive method may still further include executing the behavior modeling function of each modeled object affected by the first behavior event object trigger; and updating the modeled objects affected by the execution of the behavior modeling functions executed by said executing step.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.